PYEONGCHANG, South Korea (Reuters) - A Russian curling medalist at the Pyeongchang Winter Olympics is suspected of having tested positive for the banned substance meldonium, a source at the Games said on Sunday.

The following are five facts about the drug:

* Meldonium has been in the spotlight since Russian tennis player and former world number one Maria Sharapova tested positive for the drug in January 2016 and was later banned for 15 months. Sharapova said she was unaware that the drug had been added to the World Anti-Doping Agency’s (WADA)banned substances list.

* Meldonium is cheap and available over the counter in Russia and some eastern European countries, where it is marketed as Mildronate by the Latvian pharmaceutical firm Grindeks. It is not licensed by the Food and Drug Administration (FDA) in the United States.

* It was developed to treat patients with heart conditions such as angina, chronic heart failure, cardiomyopathy and other cardiovascular disorders. The drug also helps to adjust the body’s use of energy and can boost stamina and endurance.

* WADA placed the drug on its watch list in 2015 after mounting evidence of its performance-enhancing benefit and widespread use in various sports. It was banned on Jan. 1 2016 but WADA later said doubts over how long meldonium stayed in the body meant athletes who had tested positive for it before March 1 could have their bans reduced or overturned. In Sharapova’s case, her initial two-year ban was reduced to 15 months after the Court of Arbitration for Sport (CAS) said she “bore some degree of fault”.

* Scientist Ivars Kalvins invented meldonium in the 1970s when Latvia was still a Soviet republic. It was used to boost the stamina of Soviet troops fighting at high altitudes in Afghanistan in the 1980s, Kalvins told a Latvian newspaper in 2009.